Load Data - Warning

[sqlbullet]

We are all here because we enjoy the 10mm.  It pushes the ballistic boundaries of standard size auto-loading handgun.

In pursuit of these boundaries many forum members hand load their own ammunition.  Others reload for economy, providing generally more shots per dollar than factory ammunition.

Now for the warning.

You will often find loads in this forum which exceed published load data. I, like others have been known to exceed published data on occasion. In such situations I personally have carefully and meticulously measured to the best of my ability how my gun is behaving with a given load and observer closely for any signs on each and every cartridge that I have entered a dangerous realm.

There can be many reasons why published data stops at a given point, and those reasons are usually not disclosed in published data.  Also, each gun is an entity unto itself and may react differently.  Industry accepted margins of error are built into published data as well to account for possible extremes in environmental conditions.

The stance of the forum is to follow published load data. Exceeding such data may result in serious injury.  Maximum loads should be in new brass of quality manufacture, using load data of the same vintage as the powder.  In the absence of published starting loads, maximum loads should be reduced by 10%. The loader should work up, usually in 5 steps, checking for signs of danger or excess pressure until the maximum is reached.  If pressure signs become evident before the maximum is reached, you have reached the maximum for your gun.  Fall back to the last safe load and record it as a maximum in your data.

Since most of use do not possess equipment to carefully measure pressure other means must be used.  One of the best methods is to measure case head expansion.  Visually inspecting primers is NOT a reliable indicator of excess pressure.  Case head expansion is unique to each gun and should be tracked when working up max loads.  Any sudden change in case head measurement should be treated as an indicator of excessive pressure, and the next lower charge should be considered maximum for your gun.

Unless otherwise indicated as safe, maximum loads should not be reduced by more than 20%.  Under certain conditions, especially in large magnum rifle calibers, such excessively reduced loads can produce dangerous pressure spikes.  In handguns, the largest danger of very light loads is a bullet stuck in the barrel undetected.

You may choose to exceed published load data, stopping only when indicated by your good sense or in some cases loss of digits, eyesight and/or massive blood loss (I saw a similar statement in the most recent Handloader and couldn't help but plagiarize it).  We hope no forum members are ever injured while shooting, whether from factory ammo or hand loads.

We suggest every forum member acquire and maintain for reference a library of load data from a variety of sources and reference that data carefully anytime working up a load.   We further suggest any load you see in this forum, or any other internet forum, be carefully cross referenced against published load data before being attempted in your gun. Even if the load falls within the range of published data, follow that standard guidelines to work up to the charge.

We would ask that members as often as possible indicate loads that are over published maximums, and also indicate the source of load data they are using or used as a starting point.

Further, we ask that not only the charge, but the other components, especially primer brand and type be carefully documented.  Changing from one primer brand to another of the same type can create pressure variations of as much as 10,000 psi or more according to recent data developed by Handloader.

As always, we appreciate your contributions to our community and look forward to many your many tales regaling the great 10mm Auto cartridge!

--Mitch

[REDLINE]

Case head expansion is unique to each gun and should be tracked when working up max loads.  Any sudden change in case head measurement should be treated as an indicator of excessive pressure, and the next lower charge should be considered maximum for your gun.

--Mitch

For me a G20 is the platform (bone stock for now).

What do you use for a baseline measurement when you start out not knowing what pressure any given factory loaded round is at in the first place?  I suppose a book load of listed pressure value would be a good place to start for a baseline case head measurement?

[Turo]

Redline's question is the same as mine.  Even with very light loads, my stock G20 barrel produces case head expansion that is on the upper limits of what people consider "stopping" points.

[REDLINE]

Redline's question is the same as mine.  Even with very light loads, my stock G20 barrel produces case head expansion that is on the upper limits of what people consider "stopping" points.

That's mainly what makes me wonder.  Though my experience in case head measurement is limited.  It exists, but again is limited.

[Taterhead]

Original post is deleted. It has become clear to me that people have misunderstood, or misinterpreted my intention of this post, so I'm pulling it down. I've noticed this post referenced and/or copied in other sights and forums since I posted it, and a lot of it has been used and/or interpreted in ways that I did not intend. I still stand behind the information that I originally shared, however.

[REDLINE]

Thanks Taterhead, for a well reasoned and thorough answer based on what would seem to be extensive experience.  Much appreciated.

[sqlbullet]

Sorry for the delay in response.  This weekend largely had me away from technology.

My response would duplicate taterheads in about every way.  Buffalo Bore and Underwood both start with new starline brass, which provides a convenient factory baseline on max loads.  Measuring as you work up and looking for smiles or sudden/erratic case head readings.

[Hubcap]

If you're going to use case expansion for reading pressure, here's the method I suggest. Buy a large lot of factory ammo. Wait 6 mo. to a year to see if there are any recalls on that lot of ammo for pressure or other issues. Test a statistically significant sample of it in the test gun. Pull the bullets and primers from the remainder of the lot and use it for your own load development, again using a statistically significant sample size. This way you have a reference to a known safe standard. Make sense?

[REDLINE]

If you're going to use case expansion for reading pressure, here's the method I suggest. Buy a large lot of factory ammo. Wait 6 mo. to a year to see if there are any recalls on that lot of ammo for pressure or other issues. Test a statistically significant sample of it in the test gun. Pull the bullets and primers from the remainder of the lot and use it for your own load development, again using a statistically significant sample size. This way you have a reference to a known safe standard. Make sense?

But one still wouldn't know what safe standard they were at, right?  How would you know if it was ammo loaded to 30,000psi or 35,000psi, or whatever?  I guess I'm not understanding how that basis leads to a standard in case head measurement, except for the factory load itself that was used for the testing to begin with.  What am I misunderstanding?

[pasky2112]

Great writeup sqlbullet!

In my G20, I have found that measuring maximum case expansion around the pressure band has yielded VERY useful information about relative pressure.  By pressure band, I am referring to the circumference of the case that is a little more than 1/8" above the extraction groove. Having done several dozen unique load workups for my G20, and I have found consistent measurements that track from one workup to the next.

I have found that maximum case expansion (Using STARLINE brass) consistently measures:

Starting charges: 0.431 - 0.432"
Medium-warm: 0.433"
Book maxes: 0.433 - 0.434"
A bit beyond book maxes: 0.434"
Max acceptable expansion in my G20: 0.434"
Expansion beyond 0.434" begins to reveal Glock smiles (frowns)

Buffalo Bore and Underwood both produce ammo within SAAMI specs, but toward the upper end. They also conveniently use Starline brass. I almost exclusively use Starline brass, and it is pretty popular with 10mm handloaders. Great stuff.

Buffalo Bore loads consistently have a max case expansion of a hair hunder 0.434". That coincides with my observed upper limit in my G20.

When I do load workups, I carefully observe brass condition, and measure the expansion around the pressure band. As I approach 0.434", I know that I am getting to the maximums in my gun. I also know if I continue to push, I will get to Glock smiles, and I will have gone too far.

Examples of loads that expand to 0.434", or close to it, in my G20 chamber:

135 Nosler JHP @ 1700 fps
155 XTP @ 1425 fps
180 gr BB factory load @ 1335 fps
200 gr XTP @ 1200

Brass from my range ammo expands to about .0433". That would be a 180 @ 1175 fps.

An important consideration: different makes of brass will yield different expansion characteristics. Nickel is especially noticeable. That is one reason that I stick to Starline brass (it is also good quality and the best price). Also, that is why I do 100% of load workups in new brass. I do not use reloaded brass because work-hardened brass will expand differently than new brass.

Buffalo Bore or Underwood Ammo is a great place to start to establish an upper limit mark for those using G20 chambers. Each chamber is slightly unique, so my observations might not track with another G20 chamber. But for those reloading for a G20 barrel, most will likely find 0.434" will track consistently with max loads and/or Buffalo Bore and Underwood factory rounds. Pushing beyond that creates smiles, and loads producing smiles should be backed down.

I typically load 10 rounds per increment and increase by 0.2 or 0.3 grain increments depending upon the type of powder and how close to max. All are hand weighed and verified with check weights. At the range, I do the following routine:

Shoot one round. Holster.

Observe chrony reading.
Retrieve case.
Inspect overall condition (looking for smiles, brass flow, gas leakage at the primer pocket, primer condition, unburned powder, powder residue on case indicating poor chamber seal, etc. etc.)
Carefully measure the max expansion around the pressure band.

Chrony data, brass condition, and case expansion should track with expectations. If not, then I do not keep shooting the next charge increments. I have pulled plenty of bullets over the years.

If all is good-to-go, then rinse and repeat. For the next string, I use a different target location so that I can examine groups. This is a time-consuming process, but has enabled me to safely develop some nice ammunition.

Hi Everyone!  I recognize some of you from over @ GT.

Taterhead,
This is great info!  I am also just starting reloading for my new G20.  You give some very specific practical tips on loading for this incredible handgun.  Yet the tips are good for ANY loading for any high-power round and platform.  It seems being methodical and disciplined is the key if you chose to push envelope levels of loads such as max+ 10mm.  Do you know of or have any worthy publications or software programs that help model internal ballistics?
Thanks much and I'll be seein' y'all 'round town.   

- Dave

[pasky2112]

If you're going to use case expansion for reading pressure, here's the method I suggest. Buy a large lot of factory ammo. Wait 6 mo. to a year to see if there are any recalls on that lot of ammo for pressure or other issues. Test a statistically significant sample of it in the test gun. Pull the bullets and primers from the remainder of the lot and use it for your own load development, again using a statistically significant sample size. This way you have a reference to a known safe standard. Make sense?

How would you know what powder or primers they are using?

[sqlbullet]

Sorry if that wasn't clear.

Use the brass, not the powder/primers.  The idea being you have the same pressure vessel and it should react similarly as you reach your pressure limits.

Underwood and Buffalo Bore make this simple since they use Starline brass.  Easy enough to just buy your own brass from starline.

[Taterhead]

If you're going to use case expansion for reading pressure, here's the method I suggest. Buy a large lot of factory ammo. Wait 6 mo. to a year to see if there are any recalls on that lot of ammo for pressure or other issues. Test a statistically significant sample of it in the test gun. Pull the bullets and primers from the remainder of the lot and use it for your own load development, again using a statistically significant sample size. This way you have a reference to a known safe standard. Make sense?

But one still wouldn't know what safe standard they were at, right?  How would you know if it was ammo loaded to 30,000psi or 35,000psi, or whatever?  I guess I'm not understanding how that basis leads to a standard in case head measurement, except for the factory load itself that was used for the testing to begin with.  What am I misunderstanding?

You are right that you will not know the actual pressure number. Choose Buffalo Bore or Underwood. They are both going to be closer to the upper limit, but within SAAMI specs. They also use the same brass that many of us use - so apples-to-apples.

Hope that helps.

[Hubcap]

If you're going to use case expansion for reading pressure, here's the method I suggest. Buy a large lot of factory ammo. Wait 6 mo. to a year to see if there are any recalls on that lot of ammo for pressure or other issues. Test a statistically significant sample of it in the test gun. Pull the bullets and primers from the remainder of the lot and use it for your own load development, again using a statistically significant sample size. This way you have a reference to a known safe standard. Make sense?

But one still wouldn't know what safe standard they were at, right?  How would you know if it was ammo loaded to 30,000psi or 35,000psi, or whatever?  I guess I'm not understanding how that basis leads to a standard in case head measurement, except for the factory load itself that was used for the testing to begin with.  What am I misunderstanding?

You are right that you will not know the actual pressure number. Choose Buffalo Bore or Underwood. They are both going to be closer to the upper limit, but within SAAMI specs. They also use the same brass that many of us use - so apples-to-apples.

Hope that helps.

Sorta agreed, but still not the same lot of brass, which might give false or misleading readings.

[gandog56]

I am more into accuracy vs. speed. Since I have NEVER found the most accurate load to be around a max recipe, I don't go there. My usual 10mm reload is rather more on the low end. And they are effective.